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<p> This package contains the main interfaces that model the architecture 
  from both an application developer and a stack vendor view.</p>
         
<ul>
       <li>Application Developer View:<br>
     The application developer is concerned with implementing the 
  <it> SipListener </it> interface. This Interface defines the methods required by applications 
  to receive and process messages from a vendors SIP stack. 
 <href ="SipEvent.html"> 
     A SipProvider receives messages from the underlying SIP 
     network, which in turn encapsulates these messages as Events and passes 
     them  to its registered SipListener.</href> 
     An application must register with
     a  SipProvider to listen for Events by implementing the 
     SipListener interface.
     A single SipListener interface is mandated in the architecture.<br>
         <br>
       </li>
       <li>Stack Vendors View:<br>
     The stack vendor implements all the interfaces in this specification 
  excluding the SipListener interface, 
   however the two most important interfaces 
  from the architecture point of view are the <a href="SipStack.html">SipStack</a> 
  and the <a href="SipProvider.html">SipProvider</a> interfaces.<br></li>
                   
  <ul>
         <li>                                        
      <p>SipStack - This interface can be viewed as the stack management interface
  of the architecture. The SipStack interface encapsulates the dynamic 
management characteristics
  of the SIP stack, such as ListeningPoints which encapsulate port
 and   transport. As well as the central	
 point for the creation and querying of SipProviders in the architecture
 .&nbsp;&nbsp;</p>
  </li>
    <li>                                        
    <p>SipProvider - This interface can be viewed as the messaging
  interface of the architecture. Multiple SipProviders are allowed
  within the architecture. This interface defines the methods that allow
  an application implementing the SipListener to register with the SipProvider
  to recieve incoming requests and responses. The methods defined &nbsp;to
 send SIP messages are also defined within the SipProvider<href
 ="message/Message.html"> interface.              </href><br>
                 </p>
      </li>
       
  </ul>
     
</ul>
        <b>Messaging model:</b><br>
The architecture specifies that outgoing messages are sent via the
SipProvider and can either be of type <a href="message/Request.html">Request
</a>or <a href="message/Response.html">Response</a>. This action is initiated
by the application. Incoming messages
on the other hand are passed to an application registered to the SipProvider
and can either be of type <a href="RequestEvent.html">RequestEvent </a>or
<a href="ResponseEvent.html">ResponseEvent</a>, each containing a Request
or Response message respectively. This architecture follows the Listener/Provider event
model, which is suitable for applications that are unsure when the next event 
will arrive i.e. the applications listens for it. <br>
<br>
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